Blue inorganic pigments, such as cobalt blue (CoAl2O4), ultramarine (Na7Al6Si6O24S3), Prussian blue (Fe4[Fe(CN)6]3), and azurite (Cu3(CO3)2(OH)2), are known. However, these known compounds all suffer from environmental and/or durability issues. For example, prussian blue liberates HCN under mild acidic conditions, and ultramarine and azurite are not stable with respect to heat and acidic conditions. Additionally, commercial processes for making ultramarine produce significant SO2 emissions.